The subject of blood pressure in diabetes mellitus has aroused considerable controversy during recent years, and yet there is no unanimity of opinion on the matter at the present time. With the discrepancies in the literature in mind, a statistical study of the problem has been undertaken. Obviously, in order to make such a study, some standard must be used for comparison. In the analysis of the data presented in this paper the blood pressures of the diabetic persons are compared with those of three control series: (1) a group of dispensary patients; (2) a group of hospital patients, and (3) a so-called normal group. A necropsy series of diabetic cases is also studied. LITERATURE In 1733, Stephen Hales1performed his memorable experiment on the blood pressure of the horse, in which, after the insertion of a brass pipe into the crural artery, the "blood rose in the tube eight